nImagine a 2-D world, ÒFlatland.Ó
nFlatlanders cannot move, see, or hardly
think in more than 2-D, just as we cannot in more than 3-D.
nImagine a 3-D visitor coming to
Flatland.
nHe can see into any part of Flatland, and
can enter any part without passing thru another part.